Hexadecaflagellate swimming presents an intriguing circumstance in which the distance of separation between
flagella is so small that hydrodynamic coupling is inevitable.
When fully splayed (Fig. REF B) the 16 flagella are separated on average by \(360/16 = 22.5^\circ \) 
or \(7.85\)  \(\mu \) m measured at a radial distance of 20 \(\mu \) m from the cell, compared to \(360/8=45^\circ \)  and twice this
distance in P. octopus.
In P. cyrtoptera the interflagellar distance is thus far below the critical length to achieve synchronization by hydrodynamics [1]}.
Strong hydrodynamic interactions are evident between some or even all flagella (SI Video 8), none more so than during the pronk.
Instead of tracking individual flagella (which beat in synchrony), we use the area \({\cal A}(t)\)  bounding the flagella as proxy for phase of beat cycle (normalized):
\(\phi _{16}(t)= \left(\frac{t-t_n}{t_{n+1}-t_n}\right) \quad \quad [t_{n}\le t\le t_{n+1}]~,\) 
